Electric furnace



Nova 4- 1924,

E. A. A. GRiNWALl.

ELECTRIC FURNACE Filed Sept. 28. 192] '6 v E/VTORi itfM 8 7 Patented Nov. 4, 1924.

EUGEN ASSAR ALEXIS GRbN'WALL, OF STOGKHOLH, SWEDEN.

ELECTRIC FURNACE.

Application filed September 28, 1921. Serial No. 503,791.

To all whom it may concern:

Be it known that I, EUGEN ASSAR ALEXIS GRESNWALL, subject of the King of Sweden, residing at Stureplan 13, Stockholm, Sweden, have invented new and useful Improvements in Electric Furnaces (for which I have made application for Letters Patent in Sweden, application No. 923, filed March 11, 1921), of which the following is a specification.

In the manufacturev of pig-iron, ferroalloys, carbide, and the like,-in electric furnaces of open type, ii e. furnaces without a roof or lid, and with one or more electrodes of carbon or graphite suspended ver tically, or substantially vertically, in the furnace chamber, attempts have been made without success to protect the electrodes by different means against too rapid consumption by burning. The lower part of the electrode, which is usually heated to redness by action of the electric current passing through it and by the action of the hot gases developed during the melting process and the reaction in the furnace and arising around the electnode, is consumed rapidly, owing to the fact the air has free access to it at the same time.

The present invention has for object a device which serves to prevent to a very great extent this combustion of the electrodes.

The device consists essentially therein that the lower part of the electrode, or electrodes,

is surrounded by a protective collar, consistmg of two or more concentricwater-cooled rings of iron, copper, or other suitable metal or material, supporting between them a ring of refractory non-conductive, material, for

' example firebricksa In order to make plain the invention there is shown on the accompanying drawing, by way of example, in Fig. 1, in vertical section alohg line I-I in Fig. 2, an open electric furnace with an electrode suspended from above, provided with a protective device performed in accordance with the present invention. (The device for raising and lowering with electrode being left out.) Fig.2 shows the furnace'viewed from above.

1 designates the electric furnace chamber,-

nace chamber, and adjustably supported by suitable devices, which devices may be of any suitable construction and therefore not shown. 6 designatesa hollow cooling-ring or jacket surrounding the electrode, which ring is supplied, in a manner in itself known, with a cooling liquid, for example water or oil, through the feeding pi s 7, 8, which liquid is discharged through t' e pipes 10 and 11. In this case the channel 9 in thecooling ring is conceived to be divided into two separate semi-circular sections by.

partitions arranged between the feeding pipes 7, 8 and between the discharge pipes 10, 11. Obviously it is also possible to arrange merely one inlet and one outlet for the cooling liquid, so as to cause the liquid to flow round the entire electrode, for example by feeding it through the pipe 8 and discharging it through the pipe 7. -Around this inner cooling ring there are arranged, in accordance with the present invention, one or more cooling rings, separated from the inner rings 6 or from one another by a indicated above, filled up witha refractory electrically non-conductive material 12, for example firebricks. The outer ring 13 is, as indicated by the drawing,connected with the inner ring by stays or connecting pieces 17 and screw-bolts 18, 19 which are elecxtricallv insulated from the stays, so that the outer ring, or rings, with the aid of these stays or connecting pieces, is securely attached to and/carried by the inner ring, which in turn is supported in the required for example fireposition by means of devices suitable for the purpose, (not shown), for example with the aid of the feed and discharge pipes 7, 8 and 10, 11, which .in this case are connected with suitable supporting devices.

The charge is fed into the furnace chamber at the top and forms a free sliding or spreading surface 21 limited by the lower, outer edge 20 of the ring 13, and the lower end of the electrode enters with a suitable length into the charge.

l tricallyfrom the electrode. "Experience The advantage of this arrangement is, as aboveindicated, that the electrode is protected as completely as possible from too rapid combustion, which object is not attained if merely one inner cooling-ring, as has previously been proposed, is employed. It has in fact been necessary to construct the protective device or collar of at least two water-cooled or fluid-cooled rings, as, if merely one such cooled metal ring is employed, it is impossible to prevent the current passing from the electrode to that metal ring, and from the latter to the melting material, seeing that, for practical reasons, it is not possible to insulate the metal ring elecshows that, if the current in this way passes through the metal ring, the latter will be consumed rather rapidly, even if it is watercooled. If, on the otherhand, the protective device is constructed of two or more water-cooled rings with'a layer of brick or other similar material between them, the outer ring will always be electrically insulated from the electrode, for the brick ring, being cooled on two sides by the metal rings,

. will never acquire sufiicient heat to be electrically conductive. The protective device therefore can never be injured by short C11- cuiting of the electric current, while the outer cooling ring presses against. orcomes into contact with the charge. The gas which rises along the outer edge 20 of the protective device is by this device directed away from theelectrode, and thus'will not consume it.

The present cooling device is ,moreover attended by anothergreat advantagefor the melting process. The melting and reaction in the furnace takes place chiefly close to and under, the lower end of the electrode where the heat is greatest, and where thus the largest amount of gas is formed. The gas which, at great pressure, passes up towards the composite protective ring is thrown back by the latter into the charge, which involves a further utilization of part of the heat and reducing power of the gas.

By employing the protective device in question round one or more electrodes, the furnace will be partially covered, which entails a reduced consumption of carbon electrodes and power.

\ The above described device of a protective collar, so placed on the electrode that it follows it on rising or lowering, is moreover attended by the advantage that in'running the furnace a certain part of the charge, for example carbon, can be introduced under the electrode and be pressed down by the latter into the melting part of the charge.

In the manufacture of grey pig-iron rich in carbon, for example, the use of this method has been found very-convenient in order to induce the melted iron to absorb a suflicient quantity of carbon. This method cannot be practiced in an entirely covered furnace.

Having thus described my invention I declarethat what I claim is: 1. In an electric furnace of the open type, an electrode suspended therein, a cooling acletcomprising a pair of concentric rings surrounding said electrode, a refractory nonconducti-ve material disposed between said rings, and means connecting said rings to- EUGEN ASSAR ALEXIS GRKTNWALL Witnesses:

AUG. 'HAGELIN,

M LQ 

